Nonsense error messages on invalid aout string offset

translate_symbol_table returns false on detecting an out of range name
string offset, hooray for error checking, but doesn't set bfd_error or
print a useful error.  bfd_error therefore contains whatever it had
previously, in my testing, bfd_error_system_call.  So the error
printed depended on errno.

	PR 22887
	* aoutx.h (translate_symbol_table): Print an error message and set
	bfd_error on finding an invalid name string offset.